Ciliary dyneins are preassembled in the cytoplasm before being transported into cilia, and a family of proteins containing the PIH1 domain, PIH proteins, are involved in the assembly process. However, the functional differences and relationships between members of this family of proteins remain largely unknown. Using Chlamydomonas reinhardtii as a model, we isolated and characterized two novel Chlamydomonas PIH preassembly mutants, mot48-2 and twi1-1. A new allele of mot48 (ida10), mot48-2, shows large defects in ciliary dynein assembly in the axoneme and altered motility. A second mutant, twi1-1, shows comparatively smaller defects in motility and dynein assembly. A double mutant mot48-2; twi1-1 displays greater reduction in motility and in dynein assembly compared to each single mutant. Similarly, a double mutant twi1-1; pf13 also shows a significantly greater defect in motility and dynein assembly than either parent mutant. Thus, MOT48 (IDA10), TWI1 and PF13 may define different steps, and have partially overlapping functions, in a pathway required for ciliary dynein preassembly. Together, our data suggest the three PIH proteins function in preassembly steps that are both common and unique for different ciliary dyneins.

睫毛动力蛋白在运输到纤毛之前先在细胞质中进行组装，而包含PIH1域的蛋白质家族PIH蛋白则参与了组装过程。但是，该蛋白家族成员之间的功能差异和关系仍然未知。使用莱茵衣藻作为模型，我们分离并鉴定了两个新颖的衣藻PIH预装配突变体mot48-2和twi1-1。的新等位基因mot48（ida10），mot48-2在睫状动力蛋白，示出了大的缺陷中的轴丝和改变的运动组件。第二个突变体twi1-1表现出相对较小的运动性和动力蛋白组装缺陷。双突变体mot48-2；与每个单个突变体相比，twi1-1在运动性和动力蛋白装配方面显示出更大的降低。同样，双突变体twi1-1；pf13还显示出比任一亲代突变体在运动性和动力方面的缺陷明显更大。因此，在睫状动力蛋白预组装所需的路径中，MOT48（IDA10），TWI1和PF13可以定义不同的步骤，并具有部分重叠的功能。总之，我们的数据表明，三种PIH蛋白在预组装步骤中发挥作用，这对于不同的睫毛动力蛋白而言既常见又独特。